* Modern operating systems implement virtualization of physical memory to
efficiently use available system resources and provide inter-domain
protection through access control and isolation. The L1TF issue was found
in the way the x86 microprocessor designs have implemented speculative
execution of instructions (a commonly used performance optimisation) in
combination with handling of page-faults caused by terminated virtual to
physical address resolving process. As a result, an unprivileged attacker
could use this flaw to read privileged memory of the kernel or other
processes and/or cross guest/host boundaries to read host memory by
conducting targeted cache side-channel attacks. (CVE-2018-3620,
CVE-2018-3646)

* An industry-wide issue was found in the way many modern microprocessor
designs have implemented speculative execution of instructions past bounds
check. The flaw relies on the presence of a precisely-defined instruction
sequence in the privileged code and the fact that memory writes occur to
an address which depends on the untrusted value. Such writes cause an
update into the microprocessor’s data cache even for speculatively
executed instructions that never actually commit (retire). As a result, an
unprivileged attacker could use this flaw to influence speculative
execution and/or read privileged memory by conducting targeted cache side-
channel attacks. (CVE-2018-3693)

* A flaw named SegmentSmack was found in the way the Linux kernel handled
specially crafted TCP packets. A remote attacker could use this flaw to
trigger time and calculation expensive calls to tcp_collapse_ofo_queue()
and tcp_prune_ofo_queue() functions by sending specially modified packets
within ongoing TCP sessions which could lead to a CPU saturation and hence
a denial of service on the system. Maintaining the denial of service
condition requires continuous two-way TCP sessions to a reachable open
port, thus the attacks cannot be performed using spoofed IP addresses.
(CVE-2018-5390)